Transmission system



J. am ma@ 1,810,015

TRANSMISSION SYSTEM Filed July 3, 1929 2 Sheets-Sheet l d m 0 A Illlfw Hmmml W N n .y ik!! m N, Av d June i6, 193i.,

ATTORNEY June 16 A1931- J. L. HQGG Slms TRANSMISSION SYSTEM Filed July 3, 1929 2 Sheets-Sheet 2 nunk Patented June 16, 1931 rsiaeis JOHN L. HOG'rG, OF EAST ORANGE,

JERSEY; Assienon To BELL TELEPHONE LABORATORES, NCORPORATED',OF NEW YORK, Y., A CORPORATION OF NEW YORK x Application filed July 3,

rlhis invention relates to signal transmis-v sion systems and particularly to volume control circuits for governing thev energyA level at desired points in transmission systems.

One object of the invent-ion is to provide a signal transmission system With improved volume control circuits thatshall operate to effect a quick change in the level of transmitted energy iii a signal channel and insure the holding` of the level at a fixed pointfor a predetermined length of time aftera setting of the energy level has been made.

Another object of theinvention is toV provide transmission system having transmitting and receiving ychannels',.with improved -fmeaiis for controlling a potentiometer in the transmitting channel to maintain the energy level in suoli channell substantially constant' beyond the potentiometer and means under the control of the receiving channel for holding the potentiometer in the ltransmitting channel in any set position during a receiving period. y

A further object ofthe invention is to provide a transmitting channel ina transmission system With a potentiometer divided linto sections, means controlled from a point before the potentiometer to maintain the volume substantially constant in the transmitting channel beyond tlie potentiometer, said control means serving to effect a quick setting of the potentiometer for any change in the level of the received energy and to hold the potentiometer. in a set position for a predetermined length of time, and control means governed from a receiving channel to hold the potentiometer in a set position during a. receiving period. n

ln telephone communication systemsl transmission can only be satisfactorily effected above a fixed minimum level and below a fixed maximum level. The minimum level is determined according to the noise level and vthe maximum level is generally determined by a transmitter or some relay device in the circuit. In transmitting speechor musical programs over a telephone line to a radio broadcasting stationit is desirable to hold the i volume substantially constant in thev rimasi/fission svsrnivi 1929. serial Noysvaeza i' transmitting line without interfering with the program.

j y In accordance Withthe disclosed invention a vtransmission system'liaving a transmitting and receiving 'channel is provided with a po# `tenticmeterl in the transmitting channel to maintain the energy level4 substantially constant inl the transmitting channel beyond the potentiometer. The potentiometer is divided into sections which are controlled by relays governed in accordance With the energy level received in the transmitting channel. The potentiometer sliovvni'in the draw; ings is very similar to the potentiometer disclosed in the Vapplication of C. Mathes,

Serial No. 872,951, filed J une 22, 1999,`

'A set of three relays'v are associated With each Vpotentiometer section. V The first relay in each set serves to change the setting of the potentiometer by oneV section-When a predetermined level is reached in the transmitting channel before'tliepoteiitiometer. r[he second relay in each setfs'erves to' effect accelera tion inthe operation ofthe first relay and to insure the holding of the first relay in operative position for a predetermined length of time after the o-peration thereof. The third relay in each set of relays iscontrolled from the receiving chan'nelandA serves `to hold the potentiometer in any set positionrduring a receiving period. L i

Another `set of three relays which issimilar "in, operationv to the relays associated "with each potentiometer section is provided for changing the potentiometer from its least eHicient to its most efficient position` upon starting the transmission of any signal. The first relay of this'last mentioned set of relays serves in the released positionto place the potentiometer iii its least'eiiicient position and upon operation changes the potentiometer to its most etlicient position. The'other tvvo relays of this last mentioned set of relays operate in a vmanner similar to the second and third `relays of each set associated With the potentiometer sections.

An amplilier which is connected to the transmit-ting` channel before the potentiometer, supplies potential to two auxiliary potentiometers. The first auxiliary potentiometer operates the set of starting rela-ys and the two sets of relays associated with the first two sections of the main potentiometer. The second auxiliary potentiometer controls the sets of relays associated With the remaining main potentiometer sections. Thermionic amplifier-rectifiers which are respectively associated With each of said sets of relays are connected to different points on the auxiliary potentiometers in order to effect selective operation of the sets of relays in accordance with the energy level obtaining in the transmission channels before the main potentiometer. Each amplifier-rectifier connected to an auxiliary potentiometer effects operation of the three relays in the set associated therewith. The specific means controlled by the second relay in each set for effecting quick operation and slow release of the first relay is disclosed and claimedin an application of J. L. Hogg, Serial No. 368,955 filed June 6, 1929.

In the accompanying drawings Figures 1 and 2 disclose a volume control system constructed in accordance with the invention.

Referring to Figs. 1 and 2, a two-Wire telephone system comprising conductors 1 and 2 terminates in a hybrid coil 3 and balancing network 4. Conductors 5 and 6 of a transmitting channel and conductors 7 and 8 of a receiving channel for a four-Wire system are connected to the hybrid coil 3, as shown in Fig. 1 of the drawings. The transmitting channel is provided with volume control means to maintain the volume of the transmitted signals substantially constant. A detailed showing of the receiving channel connected to the hybrid coil is deemed unneces sary for the disclosure of this invention.

A main potentiometer 9 comprising sections 10 to 15, inclusive, is connected across the transmitting channel and is controlled in a manner to be hereinafter set forth for governing the volume level in the transmitting channel. A line amplifier 16 is provided in the transmitting channel beyond the potentiometer 4 and is controlled in accordance with the setting of the potentiometer. Seven auxiliary control circuits 17 to 23, inclusive, are provided for controlling the potentiometer V9 and the line amplifier 16. An additional auxiliary control circuit 24, Fig. 2, which is governed by the receiving channel comprising conductors and 26, is similar in construction and operation to the auxiliary control circuits 17 to 23, inclusive. The auxiliary control circuit 24 serves to maintain the potent-iometer 9 in a fixed position when the talker at the transmitting station stops to permit talking by the person at the distant station.

The control of the system disclosed is obtained from a point on the transmitting channel before the potentiometer 9. This system may be called a forward acting system. The

main contr ol circuits for the auxiliary control circuits 17 to 23, inclusive, comprise a transformer 25, the primary of Which is con nected across the transmitting channel at a point ahead of the potentiometer 9. The transformer 25 is connected to an auxiliary potentiometer 26 by means of the thermionic amplifier 27, a transformer 28 and a thermionic amplifier 29. The transformer 25 is also connected to a second auxiliary potentiometer 30 by means of the amplifier 27 and the transformer 31. The auxiliary potentiometer 26 controls the operation of the auxiliary control circuits 17, 18 and 19. The auxiliary potentiometer 30 controls the operation of the auxiliary control circuits 20, 21, 22 and 23.

inasmuch as the auxiliary control circuits 19 to 24 inclusive are similar in construction and operation, a detailed description of only one of them will be given. The auxiliary control circuit 17 comprises a thermionic rectifier tube 32 having the input circuit thereof connected across the auxiliary potentiometer 26. The potentiometer 26 is assumed to impress suflicient voltage on the auxiliary control circuit 17 'for effecting the operation thereof when a Weak voice is on the transmitting channel. The. operation of the auxiliary control circuit 17 serves to change the potentiometer 9 from its least enicient position to its most efficient position. rEhe rectifier 32 controls three relays, A, B and C. A kick-off hangover circuit D and a thermionic tube E are under the control of the relay B for assisting in operating the relays A and The relay A comprises an armature 33 which is normally in engagement with a contact member 34. The armature is adapted to be moved into engagement- With a contact member 35. Vindings 36, 37, 38 and 39 are provided for effecting operation of the relay and for holding it in an operative position. The relay B comprises an armature 40 which is normally held in engagement with a contact member 41. Upon operation of relay B the armature 40 is moved in en gagement With a contact member 42. lVindings 43 and 44 are provided for operating a relay B in the manner to be hereinafter set forth. The relay C comprises an armature 93 which is normally held in engagement with the stop member 94 and out of engagement With the contact member 95. -VlvTindings 46, 47, 48 and 49 are provided for effecting operation of the relay C.

The kick-off hangover circuit D comprises a battery 50 Which is normally shunted through a resistance element 51 when thearmature 40 of the relay B is in the release position and in engagement with the contact member 41. A condenser 52 charges through the windings 39, 44 and 49 when the armature 40 of the relay B is in transit between the Contact members 41 and 42. A

CAD

' period after the party on channel has ceased talking. The limit of the condenser 53 is provided for discharging in parallel through resistance elements 54 and 55 to control the thermionic'tubeE. Space current for tube Eenergizes the windings 38 and e8 oit the relays A andv C for a limited the transmitting hangover period is controlled by the size of the resistance elements 541 and 55. f Amore detailed description of t-lie operation of the hangover circuit will be given when the complete operation of the system is considered.

A resistance element R of relatively high value. when compared with the sections oi1 the potentiometer 9 is connected between the armature 33 of the relay A and the contact member 35. This resistance element serves to prevent opening of the transmitting channel and interruption of conversation when the armature 33 is in transit between the contact members ,34 and 35.'k The relay A serves to connect the main potentiometer 9 from its least efcientposition to its most eilicient position. When the Yarmature 33 is in engagement with contactV member 311 the input circuit for the line amplifier 16 is disconnected Jfrom the main potentiometer 9 entirely. When the armature 33 is in engagement with'the contact member 35 the input. circuit for the line amplifier 16 is connected across all sections of the main potentiometer 9. y.The-relay B as before stated controls the kick-off hangover circuit D and f the amplifier E to assist in the control of the relays Avand C. hrhe relay C is assisted by the auxiliary control circuit 24 and serves to maintain the setting of the' auxiliary control circuit 17 in a lixed position during a. receiving period.` I V The auxiliary control circuit 18 `vcomprises relays A1, B7, and C1, which are similar in construction and operation to the relays A, B and C in the auxiliary control circuit 17. The relay A7 is provided with an armature 57 which is normallyin engagement with a contact member v58 `andis adapted'to be moved into engagement with a contact inem'- ber 59. l/Vhen thearmature 57 is moved out of engagement with the contact member 58 and into engagement with the Contact member 59 thel section 10 of the main potentiometer 9 is excluded from the input circuit ci" the line amplifier 16; A resistance element R1 is connected between the contact member 59 andthe armature 57 for preventing opening of `the transmitting channel when the armature 57 is in transit between the Contact members 58 and 59. The resistance element lyis relatively large as compared with theiimpedance of a section ot the main potentiometer 9 and has a relatively small impedance as compared with the impedance of the input circuit for the line amplifier 16.

The relay B 7' Ycontrols aV kick-ofi hangover for circui'trDl and a thermionic tube E1 similar in. construction and operation to like partsl clusive, are respectively provided with re-V lays A2 to AG inclusive, which are similar in construction and operation to the relay A1 respectively controlling the potentiometer sections 11 to 15 inclusive. Resistance elements R2 to R7, inclusive, are associated respectively with the relays A2 to A, inclusive inthe same manner the resist- 'ance element R7 associated with the relay A1. Similar parts in the auxiliary control tion to the rectifier 32 in the auxiliary controly circuit 17. Two'relays A7 and B7,'wliich are similar in construction andoperation to relays A and B in auxiliary circuit'17,are operated by the rectiher 61. rlhe relay 'A7 is provided withy an armature 62 which isi adapted to engage the contact member 63 when the receiving channel is in operation. The operation of the relay A7 impresses potential from a battery 611 on conductors and 66, which are connected to the `relays C. C1, C2, C3, C4., C5 and C6 of the auxiliary control circuits 17 to 23 inclusive. f rlhe relays C, C2, etc., when in operative position and fsupplied with'potential from the battery 611 establish locking circuits for themselves and the corresponding relays A, A7, etc. rl`he relay B7 controls a kick-ofi' hangover circuit D7 andan amplifier E7 similar in cons.. .ction and operation to like parts l) and E in the auxiliary control circ-uit 17. No rrelay is provided or necessary in the auxiliary control cirouit 24 correspondingto the relay C in the auxiliary control circuit 17.

' Assuming that a weak voice is impressing voice waves'on the transniitting channelconductors 5 and 6 and' that the voltages of the peaks of this weak voice are just within the range of operation ofthe volume control circuits, potential from the transmitting channel before'the main potentiometer 9 is impressed on the auxiliary potentiometer 26 by from across the potentiometer 26 is rectified by the rtube\32L for energi'zingwindings' 37,

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43 and 47 of the relays A, B and C, respectively, in the auxiliary control circuit 17. The armature 40 of the relay B disengages the contact member 41 to open the shunt circuit through the resistance element 51 around the battery 50. Upon opening of the shunt circuit the cond iser 52 charges through windings 39, 44 and 49 of the reiays A, B and C to accelerate the operation of such relays. Furthermore, the opening of the shunt circuit around the battery impresses positive potential on the grid of the tube E from battery 50 so as to effect a sudden iiow of current through the windings 33 and 48 of the relays A and C. Accordingly, the relays A, B and C are accelerated and operated in rapid manner.

When the armature 40 of the relay B engages the contact member 42 current from the thermionic tube E through the windings 38 and 48 of the relays A and C will be increased since the resistanceelement is removed from the circuit of the battery 50 to the tube E. It is apparent that the armature 33 of t-he relay A is thrown into and held tightly in engagement with the contact member 35. In a like manner t-he armature 93 is thrown into and held in engagement with the contact member 95.

The operation of the relay A as set forth above connects the input circuit of the line amplifier' 16 across all sections of the main potentiometer 9. The operation of the relayV C connects windings 36 and 46 of the relays A and C across conductors and 66 for partially completing a holding circuit for relays A and C. The holding circuit is completed by the auxiliary control circuit 24 in case the transmitting channel 'is deenergized and a receiving period is started.

When the current from the rectifier 32 is lowered as is the case between peaks of speech, the relay B will be deenergized and released. When the armature 40 of the relay B disengages the contact member 42, the resistance element 55 is again inserted in the circuit of the battery 50 to the thermionic tube E and when the armature 40 engages the upper contact member 41 the condenser 53 discharges through the resistance elements 54 and 55 in parallel. Such discharge from the condenser 53 impresses potential on the grid of the thermionic amplifier E for maintaining current ow through the windings 38 and 48 of the relays A and C. The resistance elements 54 and 55 may be varied to control the time during which the condenser 53 discharges. The discharge of the condenser 53 controls the time during which the relays A and C will remain operated after the current flow through the rectifier 32 has fallen below the value necessary to effect operation of the relays in the auxiliary control circuit 17. Thus,

the interval of time during which the input circuit of the line amplifier 16 may be connected across the complete main potentiometer 9 after the voice energy has fallen too low to maintain its connection is under control.

If the voltage on the transmitting channel before the main potentiometer 9 falls to Zero as it may between syllables of speech of setting of the volume control apparatus will be maintained and the adjustment will not be disturbed as long as the talker proceeds. lf talking were to cease for a time longer than the hangover time of the circuit D, then the relay armatures will fall back to normal position and the line amplifier 16 will be connected to one side only of the main potentiometer 9.

1f before the lapse of the hangover period a distant talker replies, then the power of his voice effects operation of the auxiliary control circuit 24. The. auxiliary control circuit in the manner hereinbefore set forth impresses energy from the battery 64 on conductors 65 and 66 for energizing the holding circuit through the coils 36 and 46 of the relays A and C. lVhen the distant talker ceases the hang over circuit D7 of the auxiliary control circuit 24 will keep current flowing through the windings 36 and 46 of the relays A and C until the talker on the transmitting channel again resumes the conversation. The above adjustment is maintained as long as the conversation continues, unless both parties cease talkingfor a timelonger than the hangover time for the auxiliary control circuits. In such a case the voice energy of the talker on the transmitting channel would have to again establish the adjustment.

If a stronger voice is on the transmitting channelthe same process will occur as above considered in describing the operation of the volume control apparatus wheny a weak voice is on the transmitting channel. Y1f the peaks of the strong talkers speech rise live transmission units above those of the weak voice previously considered, the rectifier 70 in the auxiliary control circuit 18 will be actuated to effect operation of the relays A1, BL and C1. The relays A1, B1 and C1 operate in a manner similar to the relays A, B and C in the auxiliary control circuit 17. The relay A1 excludes the potentiometer section 10 from an input circuit of the land line amplifier 16 to reduce the volume on the transmitting channel beyond the line amplifier.

If a stronger voice comes in on the transmitting channel, the auxiliary control circuits 19 to 23 inclusive, maybe operated according to the peaks of speech to control the potentiometer sections 11 to 15 inclusive, and maintain the volume level of transmitting channel beyond the line amplifier 16 sul stantially constant. The auxiliary control circuits 19 to 23 inclusive, are similar in o1- eration to the auxiliary control circuit 17 and each auxiliary control circuit is under the control of the auxiliary circuit 24 from the ifi 5 receiving channel in the sameimanner asdescribed With respecttothe operation .of the relays A and C in the auxiliary control circuitl?.

lViodificationsin the.

Within the vspirit and scope-of `the invention and` suoli modifications are intended to be covered bythe appended claims.

What is claimed is: i f

yl. ln a transmission system, impedance lmeans for controlling-the.volume in .a signal channel, means for vautomatically controlling said impedance means vaccording to a characteristic of the signal channel to maintain the volume substantially constant at a point in said channel, and means operative upon starting the operation of said automatic means for accelerating the operation thereof.

2. In a transmission system, impedance means; for controlling the-volumev in a signal channel, means forautomatically controlling said impedancefmeans according tol a characteristic of the signalv channel to maintain the volume substantiallyfconstant at a point in said c'hannehand means operative upon starting the operation of saidautomatic means for accelerating the operation there-Y of andfor insuring` the holding of said automatic vmeans inan operated positionk for a predetermined length of time after operation thereof.

3. A transmission system havingan electrical transmitting channel, impedance meansfor controlling the volume in the trans- `initting channel, means controlled by the volume level beforeY said impedance means for automatically controlling said impedance means to maintain ythe voluine'level substantiallyconstant in the Ytiansmitting channel beyond the impedance means, andl meansopeiative upon starting. the operation :of said automatic meansfor accelerating vthe operationthereof. I j

4. A transmission systein'having 'a transmitting channel, av potentiometer-for vcontrolling the volume in the transmitting channel, means for automatically controlling said potentiometer to maintain thevolume level sul'istantially constant in the transmitting channel beyond the potentiometer, and means operative upon starting the operation of said automatic means'for accelerating the operation thereof.

5. A transmission system `having a trans- 4eration thereof.

system `and in thev ar' rangement andlocation of parts may be made f predeterminedlength. ottime after each op- 6. In a transmission system, a potentiomelter` divided into sections included in a transmitting channel, means controlled from the transmitting channel jfor governing ysaid p otentiometersections to maintain the volume ,substantiallyy constant'in the channel beyond the--potentioineter, and means operative upon vstarting the operation of said first mentioned means foracceleratingthe operation thereof. l

. 7. In aitransmissionsystem, a potentiometer divided into sections included in a transmitting channel, .means controlled from the transmitting channel yfor. governino'. said po.` tentiometersections to maintain the volume Ysubstantially constant in the channel beyond `the potentiometer, and means operative upon starting theopera-tion of said i'irst mentioned means. for accelerating the operation thereof and yfor insuring the holding of said yfirst mentioned means in a set position for a pre-l determinedlength of time aft-er operation thereof. f

8. VIn a transmissionsystem, a potentiometer divided' into sections for controlling thev volume in a transmittingv channel,-automatic means for vcontrollingthe potentiometer sections according to the energy level' received inthejtransmitting channel to maintain a .constant'voluine beyond the potentiometer,

and means operativeupon starting the operation 'of said automatic means for accelerating the operation thereof'and yfor insuringthe holding of saidautcmatic means in an operated position for al predetermined length 'ofatime after setting thereof. Q

: n.9. Ina transmission system ,having-trans init-ting and lreceiving channels, a potentiometer forcontrolling .the volume in the transmitting. channel, automatic means for controlling .said potentiometer according to the energyflevel received in said transmitting vcliannelto maintain a constant voluiiielevel beyond the potentiometenand means for holding said automatic means in any set position during a receivingl period.

10. In. axtransmittin'g system, a potentiometer `divided intosections for controlling the'volume .ina transmitting channel, autostaiit` volume beyond the potentiometer, `and meansfor holding said automatic means .in any'set positionduringa receiving period.

1l. .In atransinission :system having trans mitting :and receiving. channels', a poten iL ometer for controlling-the volume in the Vtransmitting channel, automatic means -for Acontrolling said .potentiometer according to theenergyflevel received in said transmitting vchannel to maintain a constant-volume level .beyond ,the'potentiometen means @for .accel-g -e-rating fthe operation yof `sai-d,autoiifiatic `matic means for f controlling the potentioineter sections according tothe energy level received in. said channel to maintain accn` moans, and means for holding said automatic means in any set position during a receiving period.

12. In a transmitting system, impedance means for controlling the volume in a transmitti channel, means for automatically contro ling said impedance means to maintain the volume substantially constant at il point in said transmitting channel, means for accelerating said automatic means and for insuring the holding of said automatic means in an operated position for a predetermined length of time after each operation thereof, and means for holding said automatic means in any set position during a receiving period.

13. In a transmitting system, impedance means for controlling the volume in a transmitting channel, means controlled from a point before said impedance means in the transmitting channel for automatically governing said impedance means to maintain the volume substantially constant at a point beyond the impedance means in the transmitting channel, means for insuring holding the automatic means in any set position a predetermined length of time after each operation thereof, and means forholding said automatic means in any set position during a receiving period.

14. In a transmission system, a potentiometer divided into sections included in a vtransmitting channel, a relay associated With each of said potentiometer sections, said relays serving to vary the eiiiciency of the potentiometer, means controlled from the transmitting channel for operating said relays to maintain the volume substantially constant in the transmitting channel beyond the potentiometer and control means for accelerating the operation of the first 4mentioned relays and for insuring their operation for a predetermined time after each operation thereof and comprising a second set of relays respectively associated with said firstA mentioned relays.

15. In a transmission system having a transmitting and a receiving channel, a potentiometer divided into sections included in said transmitting channel, a relay associated with each potentiometer section, said relays serving when in operative position to lower the efficiency of the potentiometer, means controlled from thetransmitting channel before the potentiometer for governing said relays to maintan the volume constant in the transmitting channel beyond the potentiometer, means comprising a second set of relays respectively associated With the potentiometer sections for accelerating the operation of the first mentioned relays and for holding the vfirst mentioned relays in operated position a predetermined length of time after each operation thereof, and a third s et of relays respectively associated vWith said potentiometer sections and operated from the receiving channel for holding said iirst set of relays-in a set position during a receiving period. v

16. In a transmission system having a transmitting and a receiving channel, a potentiometer divided into sections included in said transmitting channel, a relay associa-ted with each potentiometer section, said relays serving to vary the eiliciency of the potentiometer, means controlled from the transmitting channel for operating said relays to maintain the volume substantially constant in the transmitting channel beyond the potentiometer, means comprising a second set of relays respectively associated With the potentiometer sections for accelerating the operation of the first mentioned relays and for holding the rst mentioned relays in operated position a predetermined length of time and a third set of relays for holding said first mentioned set of relays in a set position during a receiving period.

17. In a transmission system having a transmitting and a receiving channel, a main potentiometer divided into sections included in the transmitting channel, a set of relays respectively associated With said potentiometer sections for varyingy the potentiometer setting, means comprising an amplifier and potentiometer connected to the transmitting channelv before said main potentiometer for operating said relays to control the main potentiometer sections and maintain the volume constant in the transmitting channel beyond the main potentiometer,

means for accelerating the operation of said relays and for insuring holding them in a. set position for a predetermined time after each operation thereof, and means operated from the receiving channel for holding said relays in any set position during a receiving period.

18. In a signal transmission system, a. sigg'- nal channel, a potentiometer divided into sections and included in said channel, and means comprising relays for controlling said potentiometer sections to hold the volume of the signals inthe channel substantially constant, said means serving to hold said potentiometer in its lowest'impedance position When no signals are passing through the channel and to change the potentiometer to its highest impedance position upon starting of any signals through the channel having a volume at least equal to that of a Weak talker.

In witness whereof, I hereunto subscribe my name this 28th day of J une, 1929.

JOI-IN L. HOGG. 

